Lubricating composition



United States Patent M 3,510,428 LUBRICATING COMPOSITION William Didden, Latrobe, Earl E. Fisher, Valencia, and Garnet L. Karner, Monroeville, Pa., assignors to Gulf Research & Development Company, Pittsburgh, Pa., a corporation of Delaware No Drawing. Filed Dec. 22, 1967, Ser. No. 692,633 Int. Cl. C10m 1/38; B01j 1/16 U.S. Cl. 25248.2 7 Claims ABSTRACT OF THE DISCLOSURE An oxidation-resistant composition for lubricating gasfueled engines comprises (1) a major amount of a mineral lubricating oil; (2) a small amount of a bis(hydroxy phenyl)alkane having the following structural formula:

This invention relates to the lubrication of natural gas engines, and more particularly to lubricating compositions having characteristics which suit them for use in the crankcase of natural gas engines.

Increased discoveries of natural gas and its Widespread availability have contributed to the rapid growth of engines utilizing natural gas as the fuel. Currently, gas-fueled engines are used in gas transmission service, oil fie d compressor stations, oil field pumping units, irrigation pumping stations, electric power generating plants, aluminum reduction plants, sewage disposal plants and air conditioning plants.

More extensive use of engines fueled with natural gas has encouraged manufacturers of such engines to design engines which are more efficient than prior engines. In the 1940s, for example, gas burning engines had compression ratios in the order of about 55:1 and were of low BMEP. Today, medium speed truck engines drive rotary compressors in transmission service developing up to 176 BMEP and operatewith 12:1 compression ratios. It is common practice to operate gas engines unattended for long periods of time. During this period of operation the engines are subjected to heavy variable loads, atmospheric changes of temperature including adverse moisture and dust conditions. Because of the severity of the operating conditions, lubricants for certain gas-fueled engines must possess very good oxidation stability.

While the gas-fueled engines manufactured today are greatly improved over engines of the past, todays engines being capable of operating over longer periods of time at higher output without mechanical failure, successful operation of such engines is dependent to a large extent upon the quality of the lubricant used to lubricate the engine. The lubricant must prevent bearing corrosion and should provide wear protection to cylinders, piston rings and other moving parts. In addition to these characteristics, the oil should preferably be ashless.

For many years, straight or uncompounded mineral 3,510,428 Patented May 5, 1970 oils were used to lubricate gas engines. About all that was necessary in the way of oil maintenance was to circulate the oil through a filter to remove undesirable contaminants, e.g., dirt and water, which found their way into the crankcase of the engine. In lubricating such engines, highly refined parafiinic oils were especially advantageous. By the term highly refined parafiinic oils We mean a petroleum lubricating oil which has been refined by one of the more drastic refining methods known in the art, for example, by conventional solvent extraction and aluminum chloride refining adapted to remove all or substantially all of the unsaturated and aromatic constituents of the oil. Aluminum chloride refined or solvent extracted paraffinic oils, such as the Pennsylvania oils, have provided excellent base oils for many lubricating compositions Likewise, drastically refined Mid- Continent and Gulf Coastal oils have been widely used as base oils in forming gas engine lubricants.

In addition to these refining methods, lubricating oils of high quality have been obtained by hydrogenating various charge stocks derived from Pennsylvania, Mid- Continuent, West Coast, Middle East crudes, etc. It has been known, for example, that improved lubricating properties can be obtained when the lubricating oil stocks are treated with hydrogen. Treating some lubricating oil stocks with hydrogen, for example, has resulted in obtaining stocks for making excellent multigrade lubricants, i.e., lubricants for use under a wide range of temperatures.

Regardless of the treatment to which the various charge stocks are subjected, uncompounded mineral lubricating oils are not sufiiciently resistant to oxidation to withstand the severe conditions encountered in current high-output gas engines. Uncompounded mineral lubricating oils and even some compounded mineral lubricating oils after extended use become oxidized as evidenced by an increase in their acidity, corrosivity and an increase in the viscosity of the oil.

We have discovered that a mineral lubricating oil normally tending to oxidize after use in the crankcase of a gas engine can be effectively inhibited against such undesirable changes by incorporating in a major amount of the mineral lubricating oil a small amount of each of (1) a bis(hydroxyphenyl)alkane having the following structural formula:

Where R is a substituent selected from the group consisting of hydrogen and alkyl radicals containing from 1 to 3 carbon atoms, R is a substituent selected from the group consisting of secondary and tertiary alkyl radicals containing from 4 to 8 carbon atoms and R is a substituent selected from the group consisting of alkyl radicals containing from 1 to 4 carbon atoms and (2) sulfurized diisobutylene. Thus, the lubricating composition of our invention comprises a major amount of a mineral lubricating oil normally tending to oxidize upon use in the crankcase of a gas engine and a small amount, suflicient to substantially inhibit such oxidation, of a bis(hydroxyphenyl)alkane having the structural formula shown hereinabove and sulfurized diisobutylene.

The mineral lubricating oil in which the bis(hydroxyphenyl)alkane and sulfurized diisobutylene are incorporated can be any oil having a viscosity within the range of the common lubricating oils. The mineral oil is preferably a refined or semirefined paraflinic base oil. A mineral oil which has been treated with hydrogen, because of its improved stability over the untreated oil, is particularly suitable as a lubricating oil base for preparing a lubricant to be used in a high-output gas engine. For this reason, a preferred embodiment of the invention utilizes a mineral lubricating oil which has been treated with hydrogen whereby extensive hydrogenation of the olefinic and/or aromatic constituents present in the charge stock has been effected. The hydrogen treating process may be either a hydrofinishing process or a hydrotreating process. The method by which a hydrogenated mineral lubricating oil is obtained is not a part of the present invention. The viscosity requirements of the mineral oil employed in preparing a composition of the invention will vary depending upon the type of engine in which the lubricant is to be used. Thus, various grades of oil extending from light to extra heavy oils can be employed. Oils within this range may have viscosities of about 100 to about 2500 SUS at 100 F. If desired, a blend of oils of suitable viscosity may be employed instead of a single oil by means of which any desired viscosity may be secured. The mineral oil content of the composition of the invention comprises about 90 to about 99.95 percent by weight of the total composition. The particular mineral lubricating oil as well as the exact amount of such oil employed, therefore, depends upon the characteristics desired in the final composition.

The bis(hydroxyphenyl)alkanes employed in the composition of the invention are available commercially and, therefore, neither the bis(hydroxyphenyl)alkanes nor their method of preparation constitutes any portion of the invention. The preparation of the bis(hydroxyphenyl) alkanes is disclosed in U.S. Pat. No. 2,515,907, which issued July 18, 1950 to D. R. Stevens and A. C. Dubbs. The preparation of these compounds is further disclosed in US. Pat. No. 2,570,402, which issued on Oct. 9, 1951 to D. R. Stevens and A. C. Dubbs. As disclosed in said patents, the bis(hydroxyphenyl)alkanes are prepared by condensing the corresponding phenolic compound with an aldehyde. A preferred compound, i.e., bis(Z-hydroxy-S-t-butyl-S-methylphenyl)methane for use in the composition of the invention is prepared by condensing o-tertiary-butyl-paracresol with formaldehyde, preferably its trimer, trioxane. Examples of bis(hydroxyphenyl)alkanes represented by the structural formula shown hereinabove include his 2-hydroxy-3 -t-butyl--methylphenyl methane 1, 1-bis(2-hydroxy-3-t-butyl-5-methylphenyl) ethane l, 1-bis (2-hydroxy-3-t-butyl-5-methylphenyl propane 1, l-bis 2-hydroxy-3-t-butyl-5-methylphenyl butane 1, l-bis(2-hydroxy-3-t-butyl-S-methylphenyl isobutane bis 2-hydroxy-3 -sec-butyl-S-methylphenyl methane 1, l-bis 2-hydroXy-3-t-amyl-5 -methylphenyl ethane l, 1-bis 2-hydroxy-3-t-hexyl-5 -methylphenyl propane 1,1-bis(2-hydroXy-3 -t-octyl-5-methylphenyl isob utane 1, 1-bis(2-hydroxy-3-t-butyl-5-ethylphenyl) methane 1,1-bis 2-hydroxy-3-t-butyl-5-propylphenyl) methane l, l-bis 2-hydroxy-3 ,5 -di-t-butylphenyl methane While the bis(hydroxyphenyl)alkanes as defined above are known to be useful as antioxidants in stabilizing various organic substances such as motor fuels, lubricating oils, turbine oils, transformer oils, and the like, when added thereto in relatively small amounts, these compounds possess some shortcomings when employed in the lubricating oil of a gas engine. It is, therefore, an object of the present invention to overcome the shortcomings of the bis(hydroxyphenyl)alkanes when used in a gas engine lubricating oil. The bis(hydroxyphenyl) alkane in the composition of the invention comprises about 0.05 to about 1 percent by weight based on the weight of the total lubricating composition.

The sulfurized diisobutylene used in the composition of the invention is available commercially and, therefore,

neither the sulfurized diisobutylene per se nor its method of preparation constitutes any portion of the invention. Its preparation and properties are disclosed in US. Pat. No. 2,535,705, which issued on Dec. 26, 1950 to D. R. Stevens and W. C. Starnes. As disclosed in said patent, the reaction of diisobutylene with elemental sulfur results in the formation of two isomeric compounds, one of which is a bright orange-colored crystalline solid having a melting point of about 87 C. The other compound is a reddishorange crystalline solid having a melting point of about C. Prior to separating the isomers from the reaction mixture, a crude reaction product is obtained in the form of a dark oily liquid, usually containing a small quantity of unreacted sulfur and having an odor of hydrogen sulfide. In the lubricating composition of our invention, we can use either the purified crystalline products or the crude liquid reaction product. Sulfurized diisobutylene is obtained by heating a mixture of sulfur and diisobutylene in a molar ratio of about 1 to about 5 moles of sulfur per mole of diisobutylene at a temperature of about 140 to about 350 C. under autogenic pressure for about 10 minutes to about 10 hours. The sulfurized diisobutylene has a sulfur content of about 40 to 48 percent by weight. The theoretical sulfur content of sulfurized diisobutylene whose empirical formula is C H S is about 47 percent. The sulfurized diisobutylene in the composition of the invention comprises about 0.001 to about 0.1 percent by weight based on the weight of the total lubricating composition.

The relative proportions and concentrations of the bis (hydroXyphenyDalkane and the sulfurized diisobutylene may be varied within the limits set forth for each constituent as specified hereinabove. For example, the his (hydroxyphenyDalkane may be present in amounts of about 0.05 to about 1 percent by weight while the sulfurized diisobutylene may be present in amounts of about 0.001 to about 0.1 percent by weight. In any event, the amount of the combined constituents is a small amount sufficient to substantially inhabit oxidation of lubricating oils in gas engines.

The lubricating composition of the invention can contain conventional lubricant additives, if desired, to improve other specific properties of the lubricant without departing from the scope of the invention. Thus, the lubricating composition can contain a foam suppressant, a viscosity index improver, a detergent, other oxidation inhibitors, a dye, a scenting agent and the like. These agents can be separately added to the oil or they can be added in the form of a solution which contains one or more of such additives. When such conventional additives are used they are generally added in amounts between about 0.0001 and about 5 percent by weight based on the Weight of the total composition.

In compounding the lubricating composition of the invention, the components can be admixed with each other in any order either at room temperature or at an elevated temperature. The principal requirement for satisfactory blending is through and sufficient agitation. Blending is facilitated, however, by using an elevated temperature. According to one embodiment, the mineral oil, bis(hydroxyphenyl)alkane and sulfurized diisobutylene are placed in a suitable vessel equipped with an agitating device. The contents of the vessel are then agitated preferably at a temperature of about F. until a homogeneous solution is obtained. If an additional component is employed, it can be incorporated in the oil before the oil is admixed with the bis(hydroxyphenyl)alkane and sulfurized diisobutylene or it can be introduced into the mixing vessel together with the other components.

The effectiveness of compositions of the invention in comparison with compositions containing less than all of the components is demonstrated in a Lead Corrosion Test which has been found to correlate with the condition of the lubricating oil in the engines operating on natural gas. The Lead Corrosion Test has also been used in studying lubricating oils for diesel engines and is identified as Standard Method No. 5321 of Federal Test Method Standard 791. The test method is described in a publication entitled Determining Lead Corrosivity of Lubricating Oil in Large Marine and Stationary Diesel Engines, by

The results of the comparative tests on a series of compositions are set forth in Table I. In the illustrative compositions shown in Table I, the mineral oil employed was a hydrofinished oil.

TABLE I A B G D E Make-up, percent by vol; Mineral lubricating oiL. 100 100 100 100 100 Addition agents, percent by wt.

Bis(Z-hydroxy-3-t-butyl-5-methylphenyl) methane Suliurized diisobutylene (43% S Sulfun'zed diisobutylene (46% 8)..

Inspection:

Gravity: API

Viscosity, SUS:

At 100 F Flash point, 00, Fire point. 00, Pour point, F

total acid N Sulfur, percent.

Ash, percent I After lead corrosion test, FTMS 791-5321 24 hrs.,

Pb. loss, mgJsq. in-

Cu. loss, mg./sq. in. Viscosity, SUS at 100 F Viscosity increase, percent Neutralization value, .ASTM D 664, total acid N o:

G. L. Karner, Lubricating Engineering, December 1962, pages 502-513. The duration of the test and the temperature are not specified. For purposes of the present comparisons a temperature of 325 F. and a duration of 24 hours were used. In brief, the test comprises placing 500 ml. of oil to be tested into a glass cylindrical tube approximately 13 inches high and 2% inches in diameter.

' The glass tube is open at one end. Clean dry air at a rate of 2 cubic feet per hour is introduced into the oil through a second glass tube at a point near the bottom of the glass cylinder. The air agitates the test oil in the glass cylinder and is the source of oxygen for the oxidation reaction. Two test specimens, one copper and the other lead, approximately l%" x 1%" x 1 are mounted on a stainless steel or aluminum stirrer shaft which revolves at 600 rpm. The glass cylindrical tube containing the assembly is placed in a suitable bath maintained at 325 F2 F. The lead and copper panels are weighed before and after testing and the weight loss is reported in milligrams per square inch. The copper panel serves as a catalyst. A lead loss of six milligrams or more per square inch per hour is an indication that the oil has become undesirably corrosive to lead corrodible bearings with which the oil comes in contact. The loss in the weight of the lead is desirably kept as low as possible. In addition to examining the lead and copper specimens, the viscosity and acid number of the test oil have been determined before and after the test. The increase in viscosity and the acid number are desirably kept as low as possible, the increase in viscosity preferably being less than 5 percent and the increase in total acid number preferably being less than 1.

The improved characteristics obtained with compositions of the invention (Compositions D and E) are selfevident from the data in Table I. It will be noted that when only the mineral oil was employed in the test (Composition A) the lead loss was 1135 mg. per square inch, the viscosity increase in the oil was 300% and the total acid number of the oil was 9.4. When bis(2-hydroxy-3-tbutyl-S-methylphenyl)methane and sulfurized diisobutylene were separately added to the oil, the resulting compositions (Compositions B and C) were an improvement over the uncompounded composition but the lead loss, viscosity increase and total acid number were still undesirably high. When bis(2-hydroxy-3-t-butyl-5-methylphenyDmethane and sulfurized diisobutylene were both added to the mineral oil, the resulting compositions (Compositions D and B) were surprisingly better than would have been anticipated from the results obtained with the individual components. Note in particular the total acid number of the lubricating compositions after the 24-hour test. The oil itself had an acid number of 9.4. While the addition of the bis(2-hydroxy-3-t-butyl-5-methylphenyl) methane (Composition B) resulted in an improvement (acid No. of 4.9), the addition of the sulfurized diisobutylene (Composition C) resulted in no improvement and, in fact, showed even a higher acid number (acid No. of 10.0) than that obtained with the uncompounded oil. When both additives were present, the total acid number was less than 1 (Compositions D and B).

Other lubricating compositions within the scope of the invention are illustrated in Table II.

propane 1,1-bis(2-hydroxy-3-t-butyl-5-methylphauyl) butane 1,l-bis(%-hydroxy-3-t-octyl-5-methylpl1enyl) u ane hydroxy-3,5-di-t-butylphenyl) ISOb 1,1-bis( meth ne Sulfurized diisobutylene:

We claim:

1. A gas engine lubricating composition comprising a major amount of a mineral lubricating oil normally tending to become acidic and to increase in viscosity in use and a small amount, sufficient to reduce the acid-forming and viscosity-increase tendencies of the oil, of each of (1) a bis(hydroxyphenyl)alkane having the following structural formula:

wnere R is a substituent selected from the group consisting of hydrogen and alkyl radicals containing from 1 to 3 carbon atoms, R is a substituent selected from the group consisting of secondary and tertiary alkyl radicals containing from 4 to 8 carbon atoms and R is a substituent selected from the group consisting of alkyl radicals containing from 1 to 4 carbon atoms and (2) sulfurized diisobutylene having a sulfur content of about 40 to about 48 percent by weight obtained by heating a mixture of sulfur and diisobutylene in a molar ratio of about 1 to about 5 moles of sulfur per mole of diisobutylene at a temperature of about 140 to about 350 C. under autogenic pressure for about minutes to about 10 hours.

2. The lubricating composition of claim 1 wherein the bis(hydroxyphenyl)alkane comprises about 0.05 to about 1 percent by weight of the composition and the sulfurized diisobutylene comprises about 0.001 to about 0.1 percent by weight of the composition.

3. The lubricating composition of claim 2 wherein the mineral lubricating oil has a viscosity of about 100 to about 2500 SUS at 100 F.

4. A gas engine lubricating composition comprising a major amount of a mineral lubricating oil normally tending to become acidic and to increase in viscosity in use and a small amount, sufficient to reduce the acid-forming and viscosity-increase tendencies of the oil, of each of bis(2-hydroxy-3-t-butyl 5 methylphenyl)methane and sulfurized diisobutylene having a sulfur content of about 40 to about 48 percent by weight obtained by heating a mixture of sulfur and diisobutylene in a molar ratio of about 1 to about 5 moles of sulfur per mole of diisobutylene at a temperature of about 140 to about 350 C. under autogenic pressure for about 10 minutes to about 10 hours.

5. The lubricating composition of claim 4 wherein the bis(2-hydroxy-3-t-butyl-5 methylphenyl)methane comprises about 0.05 to about 1 percent by weight of the composition and the sulfurized diisobutylene comprises about 0.001 to about 0.1 percent by Weight of the composition.

6. The lubricating composition of claim 5 wherein the mineral lubricating oil has a viscosity of about to about 2500 SUS at 100 F.

7. A gas engine lubricating composition comprising a major amount of a mineral lubricating oil, about 0.25 percent by weight of bis(2 hydroxy-3-t-butyl-5-methylphenyl)methane and about 0.01 percent by weight of sulfurized diisobutylene having a sulfur content of about 43 to about 46 percent by weight obtained by heating a mixture of sulfur and diisobutylene in a molar ratio of about 1 to about 5 moles of sulfur per mole of diisobutylene at a temperature of about to about 350 C. under autogenic pressure for about 10 minutes to about 10 hours.

References Cited UNITED STATES PATENTS 2,514,625 7/1950 Clausen et a1. 252406 X 2,535,705 12/1950 Stevens et al. 44-63 2,570,402 10/1951 Stevens et al. 25252 2,738,344 3/1956 Rogers et al. 25245 OTHER REFERENCES C. I. BONER: Gear and Transmission Lubricants, 1964, p. 80.

DANIEL E. WYMAN, Primary Examiner J. M. HICKEY, Assistant Examiner US. Cl. X.R. 252404, 406

mg UNITED STATES PATENT ()FFICE CERTIFICATE OF CORRECTION Patent No. 8 Dated May 5, 1970 Inventor-(s) William Didden, Earl E. Fisher and Garnet L. Karner It: is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

' Column 1, line 7, "Ser. No. 692,633" should read Column 2, line 22, "Continuent" should read Continent Column 4, line 38, "inhabit" should read inhibit line 57, "through" should read thorough Colunm 7, line 19, "wnere" should read where SIGN My SHIP!) slips-1970 mm 3. a. ldnnl II. Ma. 3 I fln-lniom of Patents Mam 

